U.S. patent number 10,285,187 [Application Number 15/145,729] was granted by the patent office on 2019-05-07 for methods and apparatus for multiple user uplink.
This patent grant is currently assigned to QUALCOMM Incorporated. The grantee listed for this patent is QUALCOMM Incorporated. Invention is credited to Alfred Asterjadhi, Gwendolyn Denise Barriac, George Cherian, Gang Ding, Simone Merlin, Bin Tian.
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United States Patent |
10,285,187 |
Ding , et al. |
May 7, 2019 |
Methods and apparatus for multiple user uplink
Abstract
Systems and methods are disclosed that may provide for selective
multi-user uplink (UL) of data for wireless devices. For example, a
first wireless device may request permission to initiate a UL
transmission to a second wireless device. The first wireless device
may then receive, from the second wireless device, permission to
initiate the UL transmission according to a multi-user (MU) UL
protocol, determine a threshold duration for the UL transmission,
and transmit UL data to the second wireless device according to the
MU UL protocol and the threshold duration.
Inventors: |
Ding; Gang (San Diego, CA),
Merlin; Simone (San Diego, CA), Asterjadhi; Alfred (San
Diego, CA), Cherian; George (San Diego, CA), Barriac;
Gwendolyn Denise (Encinitas, CA), Tian; Bin (San Diego,
CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
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Assignee: |
QUALCOMM Incorporated (San
Diego, CA)
|
Family
ID: |
56008872 |
Appl.
No.: |
15/145,729 |
Filed: |
May 3, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20160330755 A1 |
Nov 10, 2016 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62157307 |
May 5, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
72/1284 (20130101); H04W 74/04 (20130101); H04W
72/1226 (20130101); H04W 52/0216 (20130101); H04W
72/1289 (20130101); H04W 72/121 (20130101); Y02D
30/70 (20200801) |
Current International
Class: |
H04W
24/08 (20090101); H04W 72/12 (20090101); H04W
74/04 (20090101); H04W 52/02 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
International Search Report and Written
Opinion--PCT/US2016/030826--ISA/EPO--dated Aug. 1, 2016. cited by
applicant.
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Primary Examiner: Truong; Lan-Huong
Attorney, Agent or Firm: Paradice and Li LLP
Parent Case Text
RELATED APPLICATION
This application claims priority to U.S. Provisional Patent
Application No. 62/157,307, titled "Methods and Apparatus for
Multiple User Uplink," filed May 5, 2015, which is hereby
incorporated by reference in its entirety.
Claims
What is claimed is:
1. A method for selective multi-user uplink (UL) communications,
the method performed by a first wireless device and comprising:
receiving, from a second wireless device, permission to initiate an
UL transmission according to a multi-user (MU) UL protocol;
determining an expected duration for the UL transmission, and
indicating the expected duration to the second wireless device;
receiving, from the second wireless device, an indication of a
maximum duration for transmitting UL data; determining that the
expected duration for transmitting the UL data to the second
wireless device is less than the maximum duration; transmitting the
UL data to the second wireless device in accordance with the MU UL
protocol and the expected duration; and after transmitting the UL
data to the second wireless device, receiving a termination message
from the second wireless device that indicates all UL transmissions
have been completed.
2. The method of claim 1, wherein the expected duration is
indicated in the UL data within one data field from the group
consisting of a legacy signal (L-SIG) field, a high efficiency
signal (HE-SIG) A field, an HE-SIG B field, an HE-SIG C field, a
media access control (MAC) header, a MAC payload, and a physical
layer (PHY) delimiter.
3. The method of claim 1, wherein indicating the expected duration
comprises transmitting an end of frame (EOF) delimiter following
the UL data to indicate that all of the UL data has been
transmitted.
4. The method of claim 1, further comprising receiving an
acknowledgment (ACK) from the second wireless device after
receiving the termination message and before the maximum duration
has elapsed.
5. The method of claim 1, wherein determining the expected duration
for the UL transmission comprises calculating, based on an
estimated throughput or data rate, a time required to transmit the
UL data.
6. The method of claim 1, further comprising, after transmitting
the UL data to the second wireless device, sending a message to
retain control of a channel used for transmitting the UL data.
7. The method of claim 6, further comprising entering a low power
state after transmitting the message to retain control of the
channel used for transmitting the UL data.
8. The method of claim 1, further comprising entering a low power
state after transmitting the UL data to the second wireless
device.
9. A first wireless device, comprising: one or more processors; one
or more transceivers; and a memory storing one or more programs
comprising instructions that, when executed by the one or more
processors, cause the first wireless device to transmit uplink (UL)
data to a second wireless device in a selective multi-user UL
communication by performing operations comprising: receiving, from
the second wireless device, permission to initiate a UL
transmission according to a multi-user (MU) UL protocol;
determining an expected duration for the UL transmission and
indicating the expected duration to the second wireless device;
receiving, from the second wireless device, an indication of a
maximum duration for transmitting the UL data; determining that the
expected duration for transmitting the UL data to the second
wireless device is less than the maximum duration; transmitting the
UL data to the second wireless device in accordance with the MU UL
protocol and the maximum duration; and after transmitting the UL
data to the second wireless device, receiving a termination message
from the second wireless device that indicates all UL transmissions
have been complete.
10. The first wireless device of claim 9, wherein the expected
duration is indicated within one data field from the group
consisting of a legacy signal (L-SIG) field, a high efficiency
signal (HE-SIG) A field, an HE-SIG B field, an HE-SIG C field, a
media access control (MAC) header, a MAC payload, and a physical
layer (PHY) delimiter.
11. The first wireless device of claim 9, wherein execution of the
instructions for indicating the expected duration causes the first
wireless device to perform operations further comprising
transmitting an end of frame (EOF) delimiter following the UL data
to indicate that all of the UL data has been transmitted.
12. The first wireless device of claim 9, wherein execution of the
instructions causes the first wireless device to perform operations
further comprising receiving an acknowledgment (ACK) from the
second wireless device after receiving the termination message and
before the maximum duration has elapsed.
13. The first wireless device of claim 9, wherein execution of the
instructions causes the first wireless device to perform operations
further comprising receiving, from the second wireless device, an
indication of one or more durations for receiving an ACK from the
second wireless device.
14. The first wireless device of claim 9, wherein execution of the
instructions to determine the expected duration for the UL
transmission further causes the first wireless device to calculate,
based on an estimated throughput or data rate, a time required to
transmit the UL data.
15. The first wireless device of claim 9, wherein execution of the
instructions further causes the first wireless device to send a
message to retain control of a channel used for transmitting the UL
data.
16. The first wireless device of claim 15, wherein execution of the
instructions further causes the first wireless device to enter a
low power state after transmitting the message to retain control of
the channel used for transmitting the UL data.
17. The first wireless device of claim 9, wherein execution of the
instructions further causes the first wireless device to enter a
low power state after transmitting the UL data to the second
wireless device.
18. A non-transitory computer-readable storage medium storing one
or more programs comprising instructions that, when executed by one
or more processors of a first wireless device, cause the first
wireless device to transmit uplink (UL) data to a second wireless
device in a selective multi-user UL by performing operations
comprising: receiving, from the second wireless device, permission
to initiate a UL transmission according to a multi-user (MU) UL
protocol; determining an expected duration for the UL transmission
and indicating the expected duration to the second wireless device;
receiving, from the second wireless device, an indication of a
maximum duration for transmitting the UL data; determining that the
expected duration for transmitting the UL data to the second
wireless device is less than the maximum duration; transmitting the
UL data to the second wireless device in accordance with the MU UL
protocol and the expected duration; and after transmitting the UL
data to the second wireless device, receiving a termination message
from the second wireless device that indicates all UL transmissions
have been completed.
19. The non-transitory computer-readable storage medium of claim
18, wherein execution of the instructions to determine the expected
duration for the UL transmission further causes the first wireless
device to calculate, based on an estimated throughput or data rate,
a time required to transmit the UL data.
Description
TECHNICAL FIELD
Certain aspects of the present disclosure generally relate to
wireless communications, and more particularly, to methods and
apparatus for multiple user uplink communication in a wireless
network.
BACKGROUND OF RELATED ART
In many telecommunication systems, communications networks are used
to exchange messages among several interacting spatially-separated
devices. Networks may be classified according to geographic scope,
which could be, for example, a metropolitan area, a local area, or
a personal area. Such networks may be designated respectively as a
wide area network (WAN), metropolitan area network (MAN), local
area network (LAN), or personal area network (PAN). Networks also
differ according to the switching/routing technique used to
interconnect the various network nodes and devices (e.g., circuit
switching vs. packet switching), the type of physical media
employed for transmission (e.g., wired vs. wireless), and the set
of communication protocols used (e.g., Internet protocol suite,
SONET (Synchronous Optical Networking), Ethernet, etc.).
Wireless networks are preferable for mobile devices that have
dynamic connectivity needs and/or ad hoc (e.g., rather than fixed
topology) network architectures. Wireless networks employ
intangible physical media in an unguided propagation mode using
electromagnetic waves (e.g., radio, microwave, infra-red, optical,
etc.). Thus, wireless networks may facilitate user mobility and
rapid field deployment.
To satisfy increasing bandwidth demands for wireless communications
systems, some communication schemes may allow multiple user
terminals to communicate with a single access point using shared
channel resources while maintaining high data throughput. Given
limited communication resources, it may be desirable to reduce the
amount of traffic passing between the access point and the multiple
terminals.
SUMMARY
This Summary is provided to introduce in a simplified form a
selection of concepts that are further described below in the
Detailed Description. This Summary is not intended to identify key
features or essential features of the claimed subject matter, nor
is it intended to limit the scope of the claimed subject
matter.
Apparatus and methods are disclosed that may allow for selective
multi-user uplink (UL) of data in wireless devices. In one example,
a method for selective multi-user uplink (UL) is disclosed. The
method may include determining a presence of data for UL to a
second wireless device, requesting permission to send a UL
transmission tot the second wireless device, receiving, from the
second wireless device, permission to send the UL transmission
according to a multi-user (MU) UL protocol, determining a requested
duration for the UL transmission, transmitting at least a portion
of the data to the second wireless device according to the MU UL
protocol, and receiving an acknowledgment of the UL
transmission.
In another example, a first wireless device is disclosed. The first
wireless device may include one or more processors, one or more
transceivers, and a memory storing instructions that, when executed
by the one or more processors, cause the first wireless device to
transmit UL data to a second wireless device in a selective
multi-user UL by performing operations comprising determining a
presence of data for UL to a second wireless device, requesting
permission to send a UL transmission tot the second wireless
device, receiving, from the second wireless device, permission to
send the UL transmission according to a multi-user (MU) UL
protocol, determining a requested duration for the UL transmission,
transmitting at least a portion of the data to the second wireless
device according to the MU UL protocol, and receiving an
acknowledgment of the UL transmission.
In another example, a first wireless device for transmitting UL
data to a second wireless device in a selective multi-user UL is
disclosed. The first wireless device may include means for
determining a presence of data for UL to a second wireless device,
means for requesting permission to send a UL transmission tot the
second wireless device, means for receiving, from the second
wireless device, permission to send the UL transmission according
to a multi-user (MU) UL protocol, means for determining a requested
duration for the UL transmission, means for transmitting at least a
portion of the data to the second wireless device according to the
MU UL protocol, and means for receiving an acknowledgment of the UL
transmission.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a multiple-access multiple-input multiple-output
system with access points and user terminals.
FIG. 2 illustrates a block diagram of the access point 110 and two
user terminals 120m and 120x in a multiple-input multiple-output
system.
FIG. 3 illustrates various components that may be utilized in a
wireless device that may be employed within a wireless
communication system.
FIG. 4 shows a time diagram of an example frame exchange of an
uplink multi-user multiple-input multiple-output communication.
FIG. 5 shows a time sequence diagram of another example frame
exchange of an uplink multi-user multiple-input multiple-output
communication.
FIG. 6 shows a time sequence diagram of another example frame
exchange of an uplink multi-user multiple-input multiple-output
communication.
FIG. 7 shows a time sequence diagram of another example frame
exchange of an uplink multi-user multiple-input multiple-output
communication.
FIG. 8 shows a time sequence diagram of uplink multi-user
multiple-input multiple-output communication.
FIG. 9 shows a diagram of a request to transmit frame.
FIG. 10 shows a diagram of a clear to transmit frame.
FIG. 11 shows a diagram of another embodiment of a clear to
transmit frame.
FIG. 12 shows a diagram of another embodiment of a clear to
transmit frame.
FIG. 13 shows a diagram of another embodiment of a clear to
transmit frame.
FIG. 14 is a time sequence diagram that shows a user terminal
fragmenting its data for transmission to fit a target transmission
duration for an uplink multi-user multiple-input multiple-output
transmission during a transmission opportunity.
FIG. 15 is a time sequence diagram that shows a user terminal
decreasing its transmission data rate to fit a target transmission
duration for an uplink multi-user multiple-input multiple-output
transmission during a transmission opportunity.
FIG. 16 is a time sequence diagram that shows a user terminal
increasing its transmission data rate to fit a target transmission
duration for an uplink multi-user multiple-input multiple-output
transmission during a transmission opportunity.
FIG. 17 is a time sequence diagram that shows a user terminal
decreasing its level of aggregation to fit a target transmission
duration for an uplink multi-user multiple-input multiple-output
transmission during a transmission opportunity.
FIG. 18 is a time sequence diagram that shows a user terminal
increasing its level of aggregation to fit a target transmission
duration for an uplink multi-user multiple-input multiple-output
transmission during a transmission opportunity.
FIG. 19 is a time sequence diagram that shows a user terminal
adding fill data 1908 to fit a target transmission duration for an
uplink multi-user multiple-input multiple-output transmission
during a transmission opportunity.
FIG. 20 is a time sequence diagram that shows a user terminal
decreasing its transmission data rate, decreasing its level of
aggregation, and adding fill data to fit a target transmission
duration for an uplink multi-user multiple-input multiple-output
transmission during a transmission opportunity.
FIG. 21 is a time sequence diagram that shows a user terminal
increasing its transmission data rate, increasing its level of
aggregation, and adding fill data to fit a target transmission
duration for an uplink multi-user multiple-input multiple-output
transmission during a transmission opportunity.
FIG. 22 is a time sequence diagram that shows user terminals
concurrently transmitting data during a transmission opportunity
for a duration that fits a target transmission duration.
FIG. 23 is a flow chart of a method for changing data for
transmission or operating parameters such that a duration of an
uplink multi-user multiple-input multiple-output transmission fits
a target transmission duration.
FIG. 24 is a time sequence diagram that shows user terminals
concurrently transmitting data during a transmission opportunity,
in accordance with some example embodiments.
FIG. 25 is a time sequence diagram that shows user terminals
concurrently transmitting data during a transmission opportunity,
in accordance with some example embodiments.
FIG. 26 is a time sequence diagram that shows user terminals
concurrently transmitting data during a transmission opportunity,
in accordance with some example embodiments.
FIG. 27 is a time sequence diagram that shows user terminals
concurrently transmitting data during a transmission opportunity,
in accordance with some example embodiments.
FIG. 28 is a flow chart of an example method for selective
multi-user uplink communications.
DETAILED DESCRIPTION
Various aspects of the novel systems, apparatuses, and methods are
described more fully hereinafter with reference to the accompanying
drawings. The teachings disclosure may, however, be embodied in
many different forms and should not be construed as limited to any
specific structure or function presented throughout this
disclosure. Rather, these aspects are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the disclosure to those skilled in the art. Based on the
teachings herein one skilled in the art should appreciate that the
scope of the disclosure is intended to cover any aspect of the
novel systems, apparatuses, and methods disclosed herein, whether
implemented independently of or combined with any other aspect of
the invention. For example, an apparatus may be implemented or a
method may be practiced using any number of the aspects set forth
herein. In addition, the scope of the invention is intended to
cover such an apparatus or method which is practiced using other
structure, functionality, or structure and functionality in
addition to or other than the various aspects of the invention set
forth herein. It should be understood that any aspect disclosed
herein may be embodied by one or more elements of a claim.
Although particular aspects are described herein, many variations
and permutations of these aspects fall within the scope of the
disclosure. Although some benefits and advantages of the preferred
aspects are mentioned, the scope of the disclosure is not intended
to be limited to particular benefits, uses, or objectives. Rather,
aspects of the disclosure are intended to be broadly applicable to
different wireless technologies, system configurations, networks,
and transmission protocols, some of which are illustrated by way of
example in the figures and in the following description of the
preferred aspects. The detailed description and drawings are merely
illustrative of the disclosure rather than limiting, the scope of
the disclosure being defined by the appended claims and equivalents
thereof.
Wireless network technologies may include various types of wireless
local area networks (WLANs). A WLAN may be used to interconnect
wireless devices using well-known networking protocols. The
embodiments described herein may apply to various communication
techniques, such as Wi-Fi or, more generally, any wireless protocol
defined by the IEEE 802.11 standard.
In some aspects, wireless signals may be transmitted according to a
high-efficiency wireless (HEW) protocol (e.g., as defined by the
IEEE 802.11ax specification) using orthogonal frequency-division
multiplexing (OFDM), direct-sequence spread spectrum (DSSS)
communications, a combination of OFDM and DSSS communications, or
other schemes. Implementations of the HEW protocol may be used for
Internet access, sensors, metering, smart grid networks, or other
wireless applications. Wireless communications according to the HEW
protocol may consume less power and/or may be more robust against
signal interference (e.g., caused by objects such as humans) than
wireless communications according to other wireless protocols.
In some implementations, a WLAN may include various component
devices such as, for example, access points ("APs") and wireless
stations ("STAs"). In general, an AP serves as a hub or base
station for the WLAN and a STA serves as a client of the WLAN. For
example, a STA may be a laptop computer, a personal digital
assistant (PDA), a mobile phone, etc. In an example, a STA connects
to an AP via a wireless link (e.g., in accordance with the IEEE
802.11 standard) to obtain general connectivity to the Internet
and/or other wide area networks. In some implementations a STA may
also operate as a software-enable AP ("SoftAP").
The techniques described herein may be used for various broadband
wireless communication systems, including communication systems
that are based on an orthogonal multiplexing scheme. Examples of
such communication systems include Space Division Multiple Access
(SDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency
Division Multiple Access (OFDMA) systems, Single-Carrier Frequency
Division Multiple Access (SC-FDMA) systems, and so forth. An SDMA
system may leverage the spatial locations of user terminals to
simultaneously transmit data to multiple user terminals. A TDMA
system may allow multiple user terminals to share the same
frequency channel by dividing a communication interval into
multiple time slots, each time slot being assigned to different
user terminal. A TDMA system may implement GSM or some other
standards known in the art. An OFDMA system utilizes orthogonal
frequency division multiplexing (OFDM), which is a modulation
technique that partitions the overall system bandwidth into
multiple orthogonal sub-carriers. These sub-carriers may also be
called tones, bins, etc. With OFDM, each sub-carrier may be
independently modulated with data. An OFDM system may implement
IEEE 802.11 wireless protocols or some other standards known in the
art. An SC-FDMA system may utilize interleaved FDMA (IFDMA) to
transmit on sub-carriers that are distributed across the system
bandwidth, localized FDMA (LFDMA) to transmit on a block of
adjacent sub-carriers, or enhanced FDMA (EFDMA) to transmit on
multiple blocks of adjacent sub-carriers. In general, OFDM symbols
are signaled in the frequency domain and SC-FDMA symbols are
signaled in the time domain. A SC-FDMA system may implement
3GPP-LTE (3rd Generation Partnership Project Long Term Evolution)
or other standards.
The teachings herein may be incorporated into (e.g., implemented
within or performed by) a variety of wired or wireless apparatuses
(e.g., nodes). In some aspects, a wireless node implemented in
accordance with the teachings herein may comprise an access point
or an access terminal.
An access point ("AP") may comprise, be implemented as, or known as
a NodeB, Radio Network Controller ("RNC"), eNodeB, Base Station
Controller ("BSC"), Base Transceiver Station ("BTS"), Base Station
("BS"), Transceiver Function ("TF"), Radio Router, Radio
Transceiver Radio Base Station ("RBS"), or some other terminology.
An AP may correspond to a Basic Service Set (BSS), and two or more
APs may correspond to an Extended Service Set (ESS)
A station "STA" may also comprise, be implemented as, or known as a
user terminal, an access terminal ("AT"), a subscriber station, a
subscriber unit, a mobile station, a remote station, a remote
terminal, a user agent, a user device, user equipment, or some
other terminology. In some implementations an access terminal may
comprise a cellular telephone, a cordless telephone, a Session
Initiation Protocol ("SIP") phone, a wireless local loop ("WLL")
station, a personal digital assistant ("PDA"), a handheld device
having wireless connection capability, or some other suitable
processing device connected to a wireless modem. Accordingly, one
or more aspects taught herein may be incorporated into a phone
(e.g., a cellular phone or smartphone), a computer (e.g., a
laptop), a portable communication device, a headset, a portable
computing device (e.g., a personal data assistant), an
entertainment device (e.g., a music or video device, or a satellite
radio), a gaming device or system, a global positioning system
device, or any other suitable device that is configured to
communicate via a wireless medium.
FIG. 1 is a diagram that illustrates a multiple-access
multiple-input multiple-output (MIMO) system 100 with access points
and user terminals. For simplicity, only one access point 110 is
shown in FIG. 1. An access point is generally a fixed station that
communicates with the user terminals and may also be referred to as
a base station or other similar terminology. A user terminal or STA
may be fixed or mobile and may also be referred to as a mobile
station or a wireless device, or other similar terminology. The
access point 110 may communicate with one or more user terminals
120 at any given moment on via downlink channels and/or uplink
channels. The downlink (e.g., forward link) represents the
communication link from the access point to the user terminals, and
the uplink (e.g., reverse link) represents the communication link
from the user terminals to the access point. A user terminal may
also communicate with another user terminal using peer-to-peer
communication techniques. A system controller 130 couples to and
provides coordination and control for the access point 110 and/or
other access points in the system 100 (not shown for
simplicity).
The example embodiments recognize that one or more of the user
terminals 120 may not support SDMA signaling techniques. Thus, for
some embodiments, the AP 110 may be configured to communicate with
both SDMA and non-SDMA user terminals. This approach may
conveniently allow older versions of user terminals ("legacy"
stations) that do not support SDMA to remain deployed in an
enterprise, extending their useful lifetime, while allowing newer
SDMA user terminals to be introduced as deemed appropriate.
In example embodiments, the access point 110 may include a number
(N.sub.ap) of antennas to facilitate multiple-input (MI) downlink
transmissions and multiple-output (MO) uplink transmissions for the
system 100. A set (K) of selected user terminals 120 may
collectively provide multiple-output downlink transmissions and
multiple-input uplink transmissions for the system 100. For SDMA
communications, the number of antennas on the access point 110 may
be greater than or equal to the number of selected user terminals
120 (e.g., N.sub.ap.ltoreq.K.ltoreq.1) when the data streams for
the K user terminals are not multiplexed in code, frequency, or
time. The number of selected user terminals 120 may be greater than
the number of antennas on the access point 110 (e.g.,
K>N.sub.ap) when the data streams are multiplexed (e.g., using
TDMA, CDMA, OFDMA, and/or other multiple-access signaling
techniques). Each selected user terminal 120 may transmit
user-specific data to and/or receive user-specific data from the
access point. In general, each selected user terminal 120 may
include a number (N.sub.ut) of antennas. In some aspects, at least
some of the selected user terminals may have different numbers of
antennas.
The SDMA system 100 may be a time division duplex (TDD) system or a
frequency division duplex (FDD) system. For a TDD system, downlink
and uplink communications may operate on the same frequency band.
For an FDD system, downlink and uplink communications may operate
on different frequency bands. In some aspects, the MIMO system 100
may utilize a single carrier or multiple carriers for transmission.
Still further, in some aspects, the system 100 may implement TDMA
signaling techniques.
FIG. 2 illustrates a block diagram of the access point 110 and two
user terminals 120m and 120x of MIMO system 100. The access point
110 includes a number (N.sub.t) of antennas 224a through 224ap. The
user terminal 120m includes a number (N.sub.ut,m) of antennas
252.sub.ma through 252.sub.mu, and the user terminal 120x includes
a number (N.sub.ut,x) of antennas 252.sub.xa through 252.sub.xu.
The access point 110 may be a transmitting entity for downlink
communications and a receiving entity for uplink communications.
The user terminal 120 may be a transmitting entity for uplink
communications and a receiving entity for downlink communications.
As used herein, a "transmitting entity" may refer to an apparatus
or device capable of transmitting data via a wireless channel, and
a "receiving entity" may refer to an apparatus or device capable of
receiving data via a wireless channel. In the following
description, the subscript "dn" denotes the downlink and the
subscript "up" denotes the uplink. For example, a number (N.sub.up)
of user terminals may be selected for simultaneous transmission on
the uplink and a number (N.sub.dn) of user terminals may be
selected for simultaneous transmission on the downlink. The number
of user terminals selected for uplink transmissions may or may not
be equal to the number of user terminals selected for downlink
transmissions. In some aspects, the access point 110 and/or the
user terminal 120 may use beam-steering and/or other spatial
processing techniques to communicate wireless signals.
Each user terminal 120 selected for uplink transmission includes a
TX data processor 288 that receives traffic data from a data source
286 and control data from a controller 280. The TX data processor
288 processes (e.g., encodes, interleaves, and modulates) the
traffic data for the user terminal 120 based on the coding and
modulation schemes selected for the user terminal and generates a
stream of data symbols. A TX spatial processor 290 performs spatial
processing to convert the data symbol stream to a number
(N.sub.ut,m) of transmit symbol streams to be transmitted via the
N.sub.ut,m antennas. Each transmitter unit ("TMTR") 254 receives
and processes (e.g., converts to analog, amplifies, filters, and
frequency upconverts) a respective transmit symbol stream to
generate an uplink signal. The transmitter units 254 may output the
uplink signals for transmission via the N.sub.ut,m antennas
252.
As described above, the N.sub.up user terminals 120 may be
scheduled for simultaneous uplink transmissions. Each of these user
terminals 120 may perform spatial processing on its respective data
symbol stream and transmit its respective set of transmit symbol
streams, via an uplink channel, to the access point 110.
At the access point 110, antennas 224a through 224ap may receive
the uplink signals from the N.sub.up user terminals. Each antenna
224 provides a received signal to a respective receiver unit
("RCVR") 222. Each receiver unit 222 performs processing
complementary to that performed by transmitter unit 254 to recover
a received symbol stream. An RX spatial processor 240 performs
receiver spatial processing on the received symbol streams from the
receiver units 222 to generate uplink data symbol streams. The
receiver spatial processing may be performed in accordance with the
channel correlation matrix inversion (CCMI), minimum mean square
error (MMSE), soft interference cancellation (SIC), or some other
technique. Each recovered uplink data symbol stream is an estimate
of a data symbol stream transmitted by a respective user terminal
120. An RX data processor 242 processes (e.g., demodulates,
deinterleaves, and decodes) each recovered uplink data symbol
stream based on the modulation and coding scheme used for that
stream to obtain decoded data. The decoded data for each user
terminal may be provided to a data sink 244 for storage and/or a
controller 230 for further processing.
The access point 110 further includes a TX data processor 210 to
receive data from a data source 208, control data from a controller
230, and/or additional data from a scheduler 234. The various types
of data may be sent on different transport channels. TX data
processor 210 processes (e.g., encodes, interleaves, and modulates)
the data for each user terminal 120 based on the modulation and
coding scheme selected for that user terminal. The TX data
processor 210 may provide a respective downlink data symbol stream
for each of the Nan user terminals. A TX spatial processor 220
performs spatial processing (such as a precoding or beamforming) to
convert the downlink data symbol streams to a number (N.sub.up) if
transmit symbol streams to be transmitted via the N.sub.up
antennas. Each transmitter unit 222 receives and processes a
respective transmit symbol stream to generate a downlink signal.
The transmitter units 222 may provide the downlink signals for
transmission from via the N.sub.up antennas 224, for example to
transmit to the user terminals 120.
At each user terminal 120, antennas 252 may receive the downlink
signals from the access point 110. Each receiver unit 254 processes
a received signal from an associated antenna 252 to recover a
received symbol stream. An RX spatial processor 260 performs
receiver spatial processing on the received symbol streams from the
receiver units 254 to generate a downlink data symbol stream. The
receiver spatial processing may be performed in accordance with the
CCMI, MMSE, or some other technique. An RX data processor 270
processes (e.g., demodulates, deinterleaves and decodes) the
recovered downlink data symbol stream to obtain decoded data for
the user terminal 120.
A channel estimator 278 estimates the downlink channel response and
provides downlink channel estimates, which may include channel gain
estimates, SNR estimates, noise variance and so on. Similarly, a
channel estimator 228 estimates the uplink channel response and
provides uplink channel estimates. Controller 280 for each user
terminal typically derives the spatial filter matrix for the user
terminal based on the downlink channel response matrix H.sub.dn,m
for that user terminal. Controller 230 derives the spatial filter
matrix for the access point based on the effective uplink channel
response matrix H.sub.up,eff. The controller 280 for each user
terminal may send feedback information (e.g., the downlink and/or
uplink eigenvectors, eigenvalues, SNR estimates, and so on) to the
access point 110. The controllers 230 and 280 may also control the
operation of various processing units at the access point 110 and
user terminal 120, respectively.
FIG. 3 illustrates various components that may be utilized in a
wireless device 302 that may be employed within the wireless
communication system 100. The wireless device 302 may be an example
embodiment of the access point 110 or the user terminal 120 of FIG.
1.
The wireless device 302 may include a processor 304 which controls
operations of the wireless device 302. The processor 304 may also
be referred to as a central processing unit (CPU). Memory 306,
which may include both read-only memory (ROM) and random access
memory (RAM), provides instructions and data to the processor 304.
A portion of the memory 306 may also include non-volatile random
access memory (NVRAM). The processor 304 may perform logical and
arithmetic operations based on program instructions stored within
the memory 306. The instructions in the memory 306 may be
executable to implement the methods described herein.
The processor 304 may comprise or be a component of a processing
system implemented with one or more processors. The one or more
processors may be implemented with any combination of
general-purpose microprocessors, microcontrollers, digital signal
processors (DSPs), field programmable gate array (FPGAs),
programmable logic devices (PLDs), controllers, state machines,
gated logic, discrete hardware components, dedicated hardware
finite state machines, or any other suitable entities that can
perform calculations or other manipulations of information.
The processing system may also include machine-readable media for
storing software. Software shall be construed broadly to mean any
type of instructions, whether referred to as software, firmware,
middleware, microcode, hardware description language, or otherwise.
Instructions may include code (e.g., in source code format, binary
code format, executable code format, or any other suitable format
of code). The instructions, when executed by the one or more
processors, cause the processing system to perform the various
functions described herein.
The wireless device 302 may also include a housing 308 that may
include a transmitter 310 and a receiver 312 to allow transmission
and reception of data between the wireless device 302 and a remote
location. The transmitter 310 and receiver 312 may be combined into
a transceiver 314. A single or a plurality of transceiver antennas
316 may be attached to the housing 308 and electrically coupled to
the transceiver 314. The wireless device 302 may also include (not
shown) multiple transmitters, multiple receivers, and multiple
transceivers.
The wireless device 302 may also include a signal detector 318 that
may be used in an effort to detect and quantify the level of
signals received by the transceiver 314. The signal detector 318
may detect such signals as total energy, energy per subcarrier per
symbol, power spectral density and other signals. The wireless
device 302 may also include a digital signal processor (DSP) 320
for use in processing signals.
The various components of the wireless device 302 may be coupled
together by a bus system 322, which may include a power bus, a
control signal bus, and a status signal bus in addition to a data
bus.
Certain aspects of the present disclosure support transmitting an
uplink (UL) signal from multiple UTs to an AP. In some embodiments,
the UL signal may be transmitted in a multi-user MIMO (MU-MIMO)
system. Alternatively, the UL signal may be transmitted in a
multi-user FDMA (MU-FDMA) or similar FDMA system. Specifically,
FIGS. 4-8 illustrate uplink MU-MIMO (UL-MU-MIMO) transmissions 410A
and 410B that would apply equally to UL-FDMA transmissions. In
these embodiments, UL-MU-MIMO or UL-FDMA transmissions can be sent
simultaneously from multiple STAs to an AP and may create
efficiencies in wireless communication.
An increasing number of wireless and mobile devices put increasing
stress on bandwidth requirements that are demanded for wireless
communications systems. With limited communication resources, it
may be desirable to reduce the amount of traffic passing between
the AP and the multiple STAs. For example, when multiple terminals
send uplink communications to the access point, it may be desirable
to minimize the amount of time required to complete the uplink of
all transmissions.
FIG. 4 is a time sequence diagram 400 showing an example of an
UL-MU-MIMO protocol 400 that may be used for UL communications. As
shown in FIG. 4, with reference to FIG. 1, the AP 110 may transmit
a clear to transmit (CTX) message 402 to the user terminals 120
indicating which user terminals 120 may participate in a particular
UL-MU-MIMO TXOP. In some embodiments, the CTX message 402 may be
transmitted in a payload portion of a physical layer convergence
protocol (PLOP) protocol data units (PPDUs). An example of a CTX
frame structure is described in greater detail below with reference
to FIG. 10.
When a user terminal (UT) 120 receives a CTX message 402 from the
AP 110 (e.g., indicating that the user terminal 120 may participate
in the next UL-MU-MIMO TXOP), the user terminal 120 may initiate a
UL-MU-MIMO transmission 410. As shown in FIG. 4A, UT 120A and UT
120B may perform UL-MU-MIMO transmissions 410A and 410B,
respectively. The UL-MU-MIMO transmissions 410 and 410B may
comprise physical layer convergence protocol (PLOP) protocol data
units (PPDUs). Upon receiving the UL-MU-MIMO transmissions 410A and
410B, the AP 110 may transmit block acknowledgments (BAs) 470 to
the user terminals 120A and 120B.
Not all APs 110 or user terminals 120 may support UL-MU-MIMO or
UL-FDMA operation. A capability indication from a user terminal 120
may be indicated in a high efficiency wireless (HEW) capability
element that is included in an association request or probe request
(not shown for simplicity). For example, the HEW capability element
may include a bit indicating UL-MU-MIMO and/or UL-FDMA capability,
the maximum number of spatial streams a user terminal 120 can use
in a UL-MU-MIMO transmission, the frequencies a user terminal 120
can use in a UL-FDMA transmission, the minimum and maximum power
and granularity in the power backoff, and the minimum and maximum
time adjustment a user terminal 120 can perform.
A capability indication from an AP 110 may be indicated in a HEW
capability element that is included in an association response,
beacon or probe response (not shown for simplicity). For example,
the HEW capability element may include a bit indicating UL-MU-MIMO
and/or UL-FDMA capability, the maximum number of spatial streams a
single user terminal 120 can use in a UL-MU-MIMO transmission, the
frequencies a single user terminal 120 can use in a UL-FDMA
transmission, the required power control granularity, and the
required minimum and maximum time adjustment a user terminal 120
should be able to perform.
In one embodiment, capable user terminals 120 may request to a
capable AP to take part in the UL-MU-MIMO (or UL-FDMA) TXOP. The
request may be included in a management frame, a request to send
(RTS) message, a quality of service (QoS) frame, a power save (PS)
poll, or an RTX frame. In one aspect, an AP 110 may respond by
granting the user terminal 120 the use of the UL-MU-MIMO feature or
the AP 110 may deny the user terminal's 120 request. The AP 110 may
grant the use of the UL-MU-MIMO and the user terminal 120 may
expect a CTX message 402 at a variety of times. Additionally, once
a user terminal 120 is enabled to take part in a UL-MU-MIMO TXOP,
the user terminal 120 may be configured to operate in a particular
mode. For example, the user terminal 120 and the AP 110 may support
multiple operation modes and the AP 110 may indicate to the user
terminal 120 which mode to use in a HEW capability element, a
management frame, or in an operation element. In one aspect, a user
terminal 120 may dynamically change its operation mode and
parameters, for example, by sending a different operating element
to the AP 110. In another aspect the AP 110 may dynamically switch
its operation mode, for example, by sending an updated operating
element or a management frame to the user terminal 120, or by
sending the updated operating element or the updated management
frame in a beacon. In another aspect, the operation mode may be
determined by the AP 110 in the setup phase and may be determined
per user terminal 120 or for a group of user terminals 120. In
another aspect the operation mode may be specified per traffic
identifier (TID).
In some operation modes of UL-MU-MIMO transmissions, a user
terminal 120 may receive a CTX message from an AP 110 and
immediately send a response to the AP 110. The response may be in
the form of a clear to send (CTS) message or another type of
message. In some examples, sending the CTS message may cause user
terminals not participating in the UL-MU-MIMO TXOP to refrain from
medium access during the UL-MU-MIMO TXOP. The requirement to send
the CTS message may be indicated in the CTX message or the
requirement may be indicated in the setup phase of the
communication between the AP 110 and the user terminal 120.
FIG. 5 is a time sequence diagram 500 that, in conjunction with
FIG. 1, shows an example of an operation mode of UL-MU-MIMO
transmissions between an AP 110 and user terminals 120A and 120B.
As shown in FIG. 5, UT 120A may transmit a CTS message 408A and UT
120B may transmit a CTS message 408B in response to receiving the
CTX message 402 from the AP 110. The modulation and coding scheme
(MCS) of the CTS message 408A and the CTS message 408B may be based
on the MCS of the CTX message 402. In an example embodiment, the
CTS messages 408A and 408B may contain the same amount of bits and
the same scrambling sequence so that they may be transmitted to the
AP 110 at substantially the same time. A duration field of the CTS
messages 408A and 408B may be based on a duration field in the CTX
by removing the time for the CTX PPDU. The user terminal 120A may
send an UL-MU-MIMO transmission 410A to the AP 110 according to the
CTX message 402 and the user terminal 120B may also send an
UL-MU-MIMO transmission 410B to the AP 110 according to the CTX
message 402. The AP 110 may then send an acknowledgment (ACK)
message 475 to the user terminals 120A and 120B. In some aspects,
the ACK message 475 may include serial ACK messages sent to each
user terminal 120 or the ACK message 475 may include BAs. In some
aspects, the ACK messages 475 may be polled. Such an embodiment may
improve transmission efficiency by enabling concurrent transmission
of CTS messages 408 from multiple user terminals 120 to an AP 110),
thereby saving time and reducing the occurrence and/or effects of
interference.
FIG. 6 is a time sequence diagram 600 that, in conjunction with
FIG. 1, shows an example of an operation mode of UL-MU-MIMO
transmissions. In this embodiment, user terminals 120A and 120B may
receive a CTX message 402 from an AP 110. The CTX message 402 may
indicate a time (T) 406, following the CTX message 402, after which
the user terminals 120A and 120B may perform UL-MU-MIMO
transmissions. The time 406 may be a short interframe space (SIFS),
a point interframe space (PIFS), or another time. The time 406 may
include time offsets as indicated by the AP 110 in the CTX message
402 or via a management frame. The SIFS and PIFS time may be fixed
in a standard or may be indicated by the AP 110 in the CTX message
402 or in a management frame. The time 406 may improve
synchronization between the AP110 and the user terminals 120A and
120B and may allow the user terminals 120A and 120B sufficient time
to process the CTX message 402, and/or other messages, before
initiating their UL-MU-MIMO transmissions.
In some circumstances, a user terminal 120 may have data to upload
to the AP 110 but may not have received a CTX message 402 or
another message indicating that the user terminal 120 may initiate
an UL-MU-MIMO transmission. In one operation mode, the user
terminals 120 may not transmit data outside of an UL-MU-MIMO
transmission opportunity (TXOP) (e.g., indicated by the CTX message
402). In another operation mode, user terminals 120 may transmit
frames to the AP 110 to request a UL-MU-MIMO TXOP and may then
perform UL-MU-MIMO transmissions during the UL-MU-MIMO TXOP, for
example, upon receiving a CTX message 402 from the AP 110. In one
embodiment, a user terminal 120 may request a UL-MU-MIMO TXOP by
transmitting a request to transmit (RTX) frame to the AP 110 (e.g.,
an example RTX frame structure is described in greater detail below
with reference to FIGS. 8 and 9). In some embodiments, the user
terminal 120 may not transmit outside of an UL-MU-MIMO TXOP, except
to send an RTX frame to the AP 110.
In other embodiments, a frame sent by a user terminal 120 to
request an UL-MU-MIMO TXOP may be any frame which indicates to an
AP 110 that a user terminal 120 has data to send. The AP 110 and
the user terminal 120 may determine (e.g., during setup) that such
frames may indicate an UL-MU-MIMO TXOP request. For example, a user
terminal 120 may indicate that it has data to send using one or
more of the following: an RTS frame, a data frame or QoS Null set
to indicate more data, and/or a PS poll message. In one embodiment,
the user terminal 120 may not transmit outside an UL-MU-MIMO TXOP,
except to send frames to trigger an UL-MU-MIMO TXOP (e.g., RTS, PS
poll, or QOS null frames). In another embodiment, the user terminal
120 may indicate a request for an UL-MU-MIMO TXOP by setting bits
in the QoS control frame of an uplink data packet.
FIG. 7 is a time sequence diagram 700 showing, in conjunction with
FIG. 1, an example of UL-MU-MIMO communications including a user
terminal 120A sending an RTX message 701 to the AP 110 to request
and initialize an UL-MU-MIMO TXOP. In this embodiment, the user
terminal 120A may send an RTX message 701 to the AP 110 to request
an UL-MU-MIMO TXOP. In other embodiments, an RTX message may be
sent by the user terminal 120B. As shown in FIG. 7, the AP 110 may
respond to the RTX message 701 with a CTX message 402 granting an
UL-MU-MIMO TXOP 730 to the user terminal 120A. The CTX message 402
may also grant the UL-MU-MIMO TXOP 730 to the user terminal 120B.
Upon receiving the CTX message 402, the user terminals 120A and
120B may initiate respective UL-MU-MIMO transmissions 410A and 410B
(e.g., concurrently) to the AP 110. As described above, the user
terminal 120A may maintain its UL-MU-MIMO transmission 410A for a
duration indicated by the AP 110 in the CTX 402, and the user
terminal 120B may similarly maintain its UL-MU-MIMO transmission
410B for the same or similar duration.
In another aspect, the AP 110 may respond to the RTX message 701
with a CTS message that grants a single-user (SU) UL TXOP. In
another aspect, the AP 110 may respond to the RTX message 701 with
a frame (e.g., ACK or CTX with a special indication) that
acknowledges the reception of the RTX message 701 but does not
grant an immediate UL-MU-MIMO TXOP. In another aspect, the AP 110
may respond to the RTX message 701 with a frame that acknowledges
the reception of the RTX message 701, and grants a delayed
UL-MU-MIMO TXOP. For example, the acknowledgement frame may specify
the future start time and/or duration of the UL-MU-MIMO TXOP. In
some embodiments, the AP 110 may send a CTX message 402 to signal
start the UL-MU-MIMO TXOP at the designated time.
In another aspect, the AP 110 may respond to the RTX message 701
with an ACK or other response signal which does not grant the user
terminal 120 an UL-MU-MIMO transmission but indicates that the user
terminal 120 shall wait for a time (T) before attempting another
transmission (e.g., sending another RTX message). In this aspect
the time T may be indicated by the AP 110 in the setup phase or in
the response signal. In another aspect, an AP 110 and a user
terminal 120 may agree on a time which the user terminal 120 may
transmit a RTX message 701, RTS, PS-poll, or any other request for
a UL-MU-MIMO TXOP.
In another operation mode, user terminals 120 may transmit requests
for UL-MU-MIMO transmissions 410 in accordance with well-known
contention-based channel access protocols. The contention
parameters for user terminals 120 implementing UL-MU-MIMO may be
set to different values than for other user terminals that are not
implementing UL-MU-MIMO. In this embodiment, the AP 110 may
indicate the value of the contention parameters in a beacon, in an
association response, or through a management frame. In another
aspect, the AP 110 may provide a delay timer that prevents a user
terminal 120 from transmitting for a certain amount of time after
each successful UL-MU-MIMO TXOP or after each RTX, RTS, PS-poll, or
QoS null frame. The timer may be restarted after each successful
UL-MU-MIMO TXOP. The AP 110 may indicate the delay timer to user
terminals 120 in the setup phase or in the CTX message 402. In some
aspects, the delay timer may be different for each of the user
terminals 120. For example, the delay timer may depend on the order
of the user terminals 120 identified in the CTX message 402.
In another operational mode, the AP 110 may specify a time interval
during which the user terminals 120 are allowed to perform
UL-MU-MIMO transmissions. In one aspect, the AP 110 may indicate a
time interval during which the user terminals 120 are allowed to
send a RTX, RTS, or other message to the AP 110 to request an
UL-MU-MIMO TXOP. In this aspect, the user terminals 120 may use
well-known contention-based channel access protocols. In another
aspect, the user terminals 120 may not initiate UL-MU-MIMO
transmissions during the specified time interval, but rather the AP
110 may send a CTX or other message to the user terminals 120 to
trigger the UL-MU-MIMO transmissions.
In certain embodiments, a user terminal 120 configured for
UL-MU-MIMO may indicate to an AP 110 that it has pending uplink
data to be transmitted. In one aspect, the user terminal 120 may
send a RTS or a PS-poll to the AP 110 to request a UL-MU-MIMO TXOP.
In another embodiment, the user terminal 120 may request an
UL-MU-MIMO TXOP using a quality of service (QoS) null data frame,
for example, where the bits 8-15 of the QoS control field indicate
a non-empty queue. In this embodiment the user terminal 120 may
determine during the setup phase which data frames (e.g., RTS,
PS-poll, QoS null, etc.) may be used to request a UL-MU-MIMO TXOP
when the bits 8-15 of the QoS control field indicate a non-empty
queue. In one embodiment, the RTS, PS-poll, or QoS null frames may
include a 1 bit indication allowing or disallowing the AP 110 to
respond with a CTX message 402. In another embodiment, the QoS null
frame may include TX power information and per-TID queue
information. The TX power information and per-TID queue information
may be inserted in the two bytes of the sequence control and QoS
controls fields in a QoS null frame and the modified QoS null frame
may be sent to the AP 110 to request a UL-MU-MIMO TXOP. In another
embodiment, with reference to FIGS. 1 and 7, the user terminal 120
may send a RTX message 701 to request a UL-MU-MIMO TXOP.
As described above with reference to FIGS. 4-7, in response to
receiving an RTS, RTX, PS-poll or QoS null frame, or other trigger
frame, an AP 110 may send a CTX message 402 to at least the
requesting user terminal 120. In one embodiment, after the
transmission of the CTX message 402 and the completion of the
UL-MU-MIMO transmissions 410A and 410B, control of the wireless
medium may return to the user terminals 120A and 120B, which may
decide how to use the remaining duration of the TXOP. In another
embodiment, after the transmission of the CTX message 402 and the
completion of the UL-MU-MIMO transmissions 410A and 410B, control
of the wireless medium may return to the AP 110, and the AP110 may
use the remaining duration of the TXOP for additional UL-MU-MIMO
transmissions (e.g., by sending CTX messages 402 to user terminals
120A and 120B and/or other user terminals in the wireless
network).
FIG. 8 is a timing diagram 800 showing an example multi-user uplink
communication. The timing diagram 800 shows an exchange of wireless
messages between an AP 110 and three user terminals 120A-120C.
During the message exchange, each of the user terminals 120A-120C
may transmit a request-to-transmit (RTX) message 802A-802C to the
AP 110. Each of the RTX messages 802A-802C may indicate that the
transmitting user terminal 120A, 120B, or 120C has data available
to be transmitted to the AP 110.
Upon receiving the RTX messages 802A-820C, the AP 110 may respond
with a message indicating that the AP 110 has received each of the
RTX messages 802A-802C from the user terminals 120A-120C. As shown
in FIG. 8, the AP 110 may transmit ACK messages 803A-803C in
response to each RTX messages 802A-802C. In some embodiments, the
AP 110 may transmit a message (e.g., a CTX message) indicating that
each of the RTX messages 802A-802C has been received, but a TXOP
has not been granted for the requesting user terminals 120A-120C.
In FIG. 8, after sending the last ACK message 803C, the AP 110 may
transmit a CTX message 804. In some aspects, the CTX message 804 is
transmitted to at least the user terminals 120A-120C. In some
aspects, the CTX message 804 may be a broadcast message. The CTX
message 804 may indicate which user terminals are granted
permission to transmit data to the AP 110 during a TXOP. The CTX
message 804 may also indicate a starting time and duration of the
TXOP. For example, the CTX message 804 may indicate that the user
terminals 120A-120C should set their network allocation vectors to
be consistent with NAV 812.
At a time indicated by the CTX message 804, the three user
terminals 120A-120C may transmit data 806A-806C to the AP 110. The
data 806A-806C may be transmitted at least partially concurrently
during the TXOP. In example embodiments, the user terminals
120A-120C may transmit their respective data 806A-806C using uplink
multi-user multiple input, multiple output transmissions
(UL-MU-MIMO) or uplink frequency division multiple access (UL-FDMA)
signaling techniques.
In some aspects, user terminals 120A-120C may transmit "padded"
data such that data transmissions by each user terminal, during a
shared TXOP, are of equal or approximately equal duration. In the
message exchange of FIG. 8, the user terminal 120A may transmit pad
data 808A, the user terminal 120C may not transmit any pad data,
and the user terminal 120C may transmit pad data 808c. The
transmission of pad data ensures that each of the user terminals
120A-120C complete their respective transmissions at approximately
the same time. This may provide for a more equalized transmission
power over the duration of the TXOP, thereby optimizing AP 110
receiver efficiencies.
After the AP 110 receives the data transmissions 806A-806C from the
user terminals 120A-120C, the AP 110 may transmit acknowledgment
messages 810A-810C to each of the user terminals 120A-120C. In some
aspects, the acknowledgment messages 810A-810C may be transmitted
at least partially concurrently using either DL-MU-MIMO or DL-FDMA
signaling techniques.
FIG. 9 shows an example embodiment of an RTX frame 900. The RTX
frame 900 may include a frame control (FC) field 910, an optional
duration field 915, a transmitter address/allocation identifier
(TA/AID) field 920, a receiver address/basic service set identifier
(RA/BSSID) field 925, a TID field 930, an estimated transmission
(TX) time field 950, and a TX power field 970. The FC field 910 may
indicate a control subtype or an extension subtype. The duration
field 915 may indicate to any receiver of the RTX frame 900 to set
the network allocation vector (NAV). In one aspect, the RTX frame
900 may not have a duration field 915. The TA/AID field 920 may
indicate a source address, which may be an AID or a full MAC
address. The RA/BSSID field 925 may indicate the RA or BSSID. In
one aspect, the RTX frame 900 may not contain a RA/BSSID field 925.
The TID field 930 may indicate an access category (AC) for which a
user terminal has data. The estimated TX time field 950 may
indicate a time requested for a UL-TXOP based on an amount of time
required for a user terminal 120 to send all the data in its buffer
at the current planned MCS. The TX power field 970 may indicate the
power at which the RTX frame 900 is being transmitted and may be
used by the AP 110 to estimate the link quality and adapt the power
backoff indication in a CTX frame.
In some embodiments, before an UL-MU-MIMO communication can take
place, an AP 110 may collect information from the user terminals
120 that are participating in the UL-MU-MIMO communication. The AP
110 may optimize the collection of information from the user
terminals 120 by scheduling the UL transmissions from each of the
user terminals 120.
As discussed above, the CTX message 402 may be used in a variety of
communications. FIG. 10 is a diagram of an example of a CTX frame
1000 structure. In this embodiment, the CTX frame 1000 is a control
frame that includes a frame control (FC) field 1005, a duration
field 1010, a receiver address field 1014, a transmitter address
(TA) field 1015, a control (CTRL) field 1020, a PPDU duration field
1025, a UT info field 1030, and a frame check sequence (FCS) field
1080. The FC field 1005 indicates a control subtype or an extension
subtype. The duration field 1010 indicates to any receiver of the
CTX frame 1000 to set the network allocation vector (NAV). In some
embodiments the RA 1014 field identifies a group of UTs through a
multicast MAC address. The TA field 1015 indicates the transmitter
address or a BSSID. The CTRL field 1020 is a generic field that may
include information regarding the format of the remaining portion
of the frame (e.g., the number of UT info fields and the presence
or absence of any subfields within a UT info field), indications
for rate adaptation for the user terminals 120, indication of
allowed TID, and indication that a CTS must be sent immediately
following the CTX frame 1000. The CTRL field 1020 may also indicate
if the CTX frame 1000 is being used for UL-MU-MIMO or for UL FDMA
or both, indicating whether an Nss or Tone allocation field is
present in the UT Info field 1030. Alternatively, the indication of
whether the CTX is for UL-MU-MIMO or for UL FDMA can be based on
the value of the subtype. In some aspects, UL-MU-MIMO and UL FDMA
operations may be jointly performed by specifying to a UT both the
spatial streams to be used and the channel to be used; in this
case, the Nss indication is referred to a specific tone allocation.
The PPDU duration 1025 field indicates the duration of the
following UL-MU-MIMO PPDU that the user terminals 120 are allowed
to send. The AP 110 may determine the duration of the following
MU-MIMO PPDU that the user terminals 120 are allowed to send based
on estimated TX time fields received in at least one RTX message
from the user terminals 120.
The UT Info 1030 field contains information regarding a particular
UT and may include a per-UT (per user terminal 120) set of
information (see UT Info 1 1030 and UT Info N 1075). The UT Info
1030 field may include an AID or MAC address field 1032 which
identifies a UT, a number of spatial streams field (Nss) 1034 field
which indicates the number of spatial streams a UT may use (in an
UL-MU-MIMO system), a Time Adjustment 1036 field which indicates a
time that a UT should adjust its transmission compared to the
reception of a trigger frame (the CTX in this case), a Power
Adjustment 1038 field which indicates a power backoff a UT should
take from a declared transmit power, a Tone Allocation 1040 field
which indicates the tones or frequencies a UT may use (in a UL-FDMA
system), an Allowed TID 1042 field which indicates the allowable
TID, an Allowed TX Mode 1044 field which indicates the allowed TX
modes, and a MCS 1046 field which indicates the MCS the UT should
use. A user terminal 120 receiving a CTX with a Allowed TID 1042
indication may be allowed to transmit data only of that TID, data
of the same or higher TID, data of the same or lower TID, any data,
or only data of that TID first, then if no data is available, data
of other TIDs. The FCS 1080 field indicates the carries an FCS
value used for error detection of the CTX frame 1000.
FIG. 11 shows another example of a CTX frame 1100 structure. In
this embodiment and in conjunction with FIG. 10, the UT Info 1030
field does not contain the AID or MAC Address 1032 field and
instead the CTX frame 1000 includes a group identifier (GID) 1026
field which identifies the UTs by a group identifier rather than an
individual identifier. FIG. 12 shows yet another example of a CTX
frame 1200 structure. The CTX frame 1200 includes a RA 1014 field
(e.g., in lieu of the GID 1026 field shown in FIG. 11) which
identifies a group of UTs through a multicast MAC address.
FIG. 13 shows an example embodiment of a CTX frame 1300 structure.
In this embodiment, the CTX frame 1300 is a management frame that
includes a Management MAC Header 1305 field, a Body 1310 field, and
a FCS 1380 field. The Body 1310 field includes an IE ID 1315 field
which identifies an information element (IE), a LEN 1320 field
which indicates the length of the CTX frame 1300, a CTRL 1325 field
which includes the same information as the CTRL 1020 field, a PPDU
Duration 1330 field which indicates the duration of the following
UL-MU-MIMO PPDU that the user terminals 120 are allowed to send, a
UT Info 1 1335 field and a MCS 1375 field which can indicate the
MCS for all the UTs to use in the following UL-MU-MIMO
transmission, or an MCS backoff for all the UTs to use in the
following UL-MU-MIMO transmission.
The UT Info 1 1335 (along with UT Info N 1370) field represents a
per-UT field that includes AID 1340 field which identifies a UT, a
number of spatial streams field (Nss) 1342 field which indicates
the number of spatial streams a UT may use (in an UL-MU-MIMO
system), a Time Adjustment 1344 field which indicates a time that a
UT should adjust its transmission compared to the reception of a
trigger frame (the CTX in this case), a Power Adjustment 1348 field
which indicates a power backoff a UT should take from a declared
transmit power, a Tone Allocation 1348 field which indicates the
tones or frequencies a UT may use (in a UL-FDMA system), an Allowed
TID 1350 field which indicates the allowable TID, and a TX start
time field 1048 which indicates a start time for the UT to transmit
uplink data.
In one embodiment, the CTX frame 1000 or the CTX frame 1300 may be
aggregated in an A-MPDU to account for a processing time of a user
terminal 120 (e.g., before initiating uplink transmissions). In
this embodiment, pad data may be added after the CTX frame to allow
a user terminal 120 additional time to process the incoming packet.
One benefit to padding a CTX frame may be to avoid possible
contention issues for the UL transmissions from other user
terminals 120 (e.g., compared to increasing the interframe space
(IFS) as described above). In one aspect, the CTX frame may be a
management frame, and may be transmitted with additional padding
information elements (IEs). In another aspect, the CTX frame may be
aggregated in an A-MPDU, and may include additional A-MPDU padding
delimiters. Padding delimiters may be provided as end of frame
(EoF) delimiters (e.g., 4 bytes) or other padding delimiters. In
another aspect, the padding may be achieved by adding data,
control, and/or Management MPDUs, as long as they do not need to be
processed within an IFS response time. The MPDUs may include
information indicating to the receiver that no immediate response
is required and will not be required by any of the following MPDUs.
In another aspect, the user terminals 120 may request a minimum
duration or padding for the CTX frame. In another embodiment, the
padding may be achieved by adding PHY OFDMA symbols, which may
include undefined bits that do not carry information (e.g., or may
include bit sequences that carry information, as long as the
information does not need to be processed within the IFS time).
In some embodiments, the AP 110 may initiate a CTX transmission. In
one embodiment, the AP 110 may send a CTX message 402 in accordance
with regular enhanced distribution channel access (EDCA) contention
protocol. In another embodiment, the AP 110 may send a CTX message
402 at scheduled times. For example, the scheduled times may be
provided in a restricted access window (RAW) indication in a beacon
frame broadcast by the AP 110 to the user terminals 120. The RAW
indication may specify a time reserved for a group of user
terminals 120 to access the medium, a target wake time (TWT)
agreement with each user terminal 120 (e.g., which may indicate to
multiple user terminals 120 to be awake at the same time to take
part in a UL-MU-MIMO transmission), or information in other fields.
Outside the RAW and/or TWT a user terminal 102 may be allowed to
transmit any frame, or only a subset of frames (e.g., non-data
frames). In some embodiments, the user terminal 102 may be
prohibited from transmitting certain frames (e.g., data frames)
outside the RAW and/or TWT. In some aspects, the user terminal 120
may indicate that it is in a sleep state. By scheduling CTX
transmissions, multiple user terminals 120 may be allocated to the
same TWT or the same RAW time.
Referring back to FIGS. 4-6, in conjunction with FIG. 1, the
UL-MU-MIMO transmissions 410A and 410B may have the same duration.
The user terminals 120 may plan to transmit data and may send a
message (e.g., an RTX) to the AP 110 requesting to transmit their
data. The AP 110 may send a message (e.g., CTX message 402) to the
user terminals 120 indicating a target transmission duration for
the UL-MU-MIMO transmissions 410A and 410B. In some aspects, the
target transmission duration may be negotiated by the AP 110 and
the user terminals 120 in the setup phase. The user terminal 120
may determine a planned transmission duration based on an amount of
data to be transmitted (e.g., as planned data) and the operating
and transmission parameters of the user terminal 120 (e.g., level
of aggregation and MCS). The user terminal 120 may determine
whether the planned transmission duration fits, exceeds, or falls
shown of the target transmission duration. In some circumstances,
the user terminal 120 may have planned data for transmission that,
when transmitted, will have a planned transmission duration that
fits (e.g., is equal to) the target transmission duration such that
the user terminal 120 may transmit its data without modification.
In other circumstances, the user terminal 120 may have planned data
for transmission that, when transmitted, would have a planned
transmission duration that exceeds the target transmission
duration. In such circumstances the user terminal 120 may change
the planned data or its operating and transmission parameters, for
example, by decreasing the amount of planned data to be transmitted
such that the planned transmission duration is within the target
transmission duration. In other circumstances, the user terminal
120 may have planned data for transmission that, when transmitted,
would have a planned transmission duration that falls short of the
target transmission duration. In such circumstances the user
terminal 120 may change the planned data or its operating or
transmission parameters, for example, by increasing the amount of
planned data to be transmitted such that the planned transmission
duration is substantially equal to the target transmission
duration.
In some aspects, the AP 110 may restrict the parameters that can be
modified by the user terminals 120. For example, the AP 110 may
indicate such restrictions in a trigger frame. In one aspect, the
AP 110 may specify a target transmission duration for the user
terminals 120, and each user terminal 120 may determine their
respective UL PPDU durations, data payload size, MCS, and amount of
fill data. In another aspect, the AP 110 may specify a target
transmission duration and a UL PPDU duration for the user terminals
120, and each user terminal 120 may determine its respective data
payload size, MCS, and amount of fill data. In another aspect, the
AP 110 may specify a target transmission duration, UL PPDU
duration, and MCS for the user terminals 120, and each user
terminal 120 may adjust its respective data payload size and amount
of fill data.
In some aspects, the user terminals 120 may send information to the
AP 110 indicating their respective data payload sizes. In one such
aspect, the AP 110 may determine an amount of fill data for each
user terminal 120 based on the data payload sizes of the user
terminals 120. In the trigger frame, the AP 110 may indicate an
amount of fill data to use, a target transmission duration, a UL
PPDU duration, and an MCS for each of the user terminals 120. In
this aspect, each of the user terminals 120 may determine their
data payload size. In another such aspect, the AP 110 may indicate
a target transmission duration, a UL PPDU duration, data payload
size, MCS, and an amount of fill data for each of the user
terminals 120. In another aspect, the AP 110 may indicate a level
of data aggregation for each user terminal 120 to use as discussed
further discussed below. Accordingly, the user terminals 120 may
determine operating and transmission parameter adjustments which
are not specified by the AP 110 in the trigger frame. FIGS. 14-22
show examples of changes that user terminals 120 may make to their
data for transmission or their operating and transmission
parameters in order to satisfy a target transmission duration.
FIG. 14 is a time sequence diagram 1400 that shows a user terminal
120 fragmenting its planned data for transmission to fit a target
transmission duration 1420 for a UL-MU-MIMO transmission during a
transmission opportunity. The dashed arrows in FIG. 14 indicate
that a duration of a first PPDU 1410A as transmitted by the user
terminal 120 remains the same as a planned transmission duration of
a first portion of the data for transmission 1406A. As described
above, an AP 110 may indicate the target transmission duration 1420
in a message (e.g., CTX message) granting a transmission
opportunity to the user terminal 120. As shown in FIG. 14, the user
terminal 120 may have planned data for transmission 1406 that has a
planned transmission duration that exceeds the target transmission
duration 1420. The user terminal 120 may modify the planned data
1406 to fit the target transmission duration 1420, for example, by
fragmenting the planned data 1406 into a first portion of data
1406A and a second portion of data 1406B. The first PPDU 1410A may
include the first portion of data 1406A and, when transmitted by
the user terminal 120 according to a UL-MU-MIMO operating mode, has
a transmission duration that falls within the target transmission
duration 1420. The second portion of data 1406B may be transmitted
by the user terminal 120 in a second PPDU 1410B, at a later time
(e.g., during a subsequent transmission opportunity). As such, the
user terminal 120 may build the first PPDU 1410A such that the
length of the PPDU coincides with the target transmission duration
indicated by the AP 110.
FIG. 15 is a time sequence diagram 1500 that shows a user terminal
120 decreasing its transmission data rate to fit a target
transmission duration 1520 for a UL-MU-MIMO transmission during a
transmission opportunity. The dashed arrows in FIG. 15 indicate an
increase in transmission duration resulting from the user terminal
120 decreasing its planned transmission data rate. As described
above, an AP 110 may indicate the target transmission duration 1520
in a message granting a transmission opportunity (e.g., trigger
frame or CTX message) to the user terminal 120. As shown in FIG.
15, the user terminal 120 may have planned data for transmission
1506 that, when transmitted according to planned operating and
transmission parameters, has a planned transmission duration that
falls short of the target transmission duration 1520. Accordingly,
the user terminal 120 may modify its operating and transmission
parameters to fit the target transmission duration 1520. For
example, the user terminal 120 may transmit the data 1506 at a
lower data rate to fit the target transmission duration 1520. The
user terminal 120 may also adjust a coding scheme and a guard
interval for the transmission of uplink data. As described above,
the AP 110 may determine and indicate the MCS adjustment for each
user terminal 120 by transmitting trigger frames (not shown for
simplicity) to the user terminals 120. Alternatively, each user
terminal 120 may determine its own MCS adjustment. The data 1506
may be provided in a PPDU 1510 that, when transmitted by the user
terminal 120 at the lower data rate according to a UL-MU-MIMO
operating mode, has a transmission duration that fits the target
transmission duration 1520.
FIG. 16 is a time sequence diagram 1600 that shows a user terminal
120 increasing its transmission data rate to fit a target
transmission duration 1620 for a UL-MU-MIMO transmission during a
transmission opportunity. The dashed arrows in FIG. 16 indicate a
decrease in transmission duration resulting from the user terminal
120 increasing the transmission data rate of the data for
transmission 1606 to produce the PPDU 1610 as transmitted by the
user terminal 120. As described above, an AP 110 may indicate the
target transmission duration 1620 in a message (e.g., CTX message)
granting a transmission opportunity to the user terminal 120. As
shown in FIG. 16, the user terminal 120 may have planned data for
transmission 1606 that has a planned transmission duration that
exceeds the target transmission duration 1620. The user terminal
120 may transmit the data 105 at a higher data rate to fit the
target transmission duration 1520. The user terminal 120 may also
adjust a coding scheme and a guard interval for the transmission of
uplink data. As described above, the AP 110 may determine and
indicate the MCS adjustment for each user terminal 120 by
transmitting trigger frames (not shown for simplicity) to the user
terminals 120. Alternatively, each user terminal 120 may determine
its own MCS adjustment. The data 1606 may be provided in a PPDU
1610 that, when transmitted by the user terminal 120 at the higher
data rate according to a UL-MU-MIMO operating mode, has a
transmission duration that fits the target transmission duration
1620.
FIG. 17 is a time sequence diagram 1700 that shows a user terminal
120 decreasing its level of aggregation to fit a target
transmission duration 1720 for a UL-MU-MIMO transmission during a
transmission opportunity. The dashed arrows in FIG. 17 indicate an
increase in transmission duration resulting from the user terminal
120 decreasing the level of aggregation for the data for
transmission 1706 to produce the PPDU 1710 as transmitted by the
user terminal 120. As described above, an AP 110 may indicate the
target transmission duration 1720 in a message (e.g., CTX message)
granting a transmission opportunity to the user terminal 120. As
shown in FIG. 17, the user terminal 120 may have planned data for
transmission 1706 that has a planned transmission duration that
falls short of the target transmission duration 1720. The user
terminal 120 may decrease a level of data aggregation in a media
access control (MAC) protocol data unit (A-MPDU) or a level of data
aggregation in a MAC service data unit (A-MSDU) to fit the target
transmission duration 1720. The AP 110 may determine and indicate
the level of aggregation for each user terminal 120 by transmitting
trigger frames (not shown for simplicity) to the user terminals
120. Alternatively, each user terminal 120 may determine its own
level of aggregation. The data 1706 may be provided in a PPDU 1710
that, when transmitted by the user terminal 120 at the lower level
of data aggregation according to a UL-MU-MIMO operating mode, has a
transmission duration that fits the target transmission duration
1720.
FIG. 18 is a time sequence diagram 1800 that shows a user terminal
120 increasing its level of aggregation to fit a target
transmission duration 1820 for a UL-MU-MIMO transmission during a
transmission opportunity. The dashed arrows in FIG. 18 indicate a
decrease in transmission duration resulting from the user terminal
120 increasing the level of aggregation for the planned data for
transmission 1806 to produce the PPDU 1810 as transmitted by the
user terminal 120. As described above, an AP 110 may indicate the
target transmission duration 1820 in a message (e.g., CTX message)
granting a transmission opportunity to the user terminal 120. As
shown in FIG. 18, the user terminal 120 may have data for
transmission 1806 that has a planned transmission duration that
exceeds the target transmission duration 1820. The user terminal
120 may increase a level of data aggregation in an A-MPDU or a
level of data aggregation in an A-MSDU to fit the target
transmission duration 1820. The AP 110 may determine and indicate
the level of aggregation for each the user terminal 120 by
transmitting trigger frames to the user terminals 120.
Alternatively, each user terminal 120 may determine its own level
of aggregation. The data 1706 may be provided in a PPDU 1810 that,
when transmitted by the user terminal 120 at the higher level of
data aggregation according to a UL-MU-MIMO operating mode, has a
transmission duration that fits the target transmission duration
1820.
FIG. 19 is a time sequence diagram 1900 that shows a user terminal
120 adding fill data 1908 to fit a target transmission duration
1920 for a UL-MU-MIMO transmission during a transmission
opportunity. The dashed arrows in FIG. 19 indicate that the
transmission duration of a PPDU 1910 as transmitted by the user
terminal 120 remains the same as the data for transmission 1906,
but the fill data 1908. As described above, an AP 110 may indicate
the target transmission duration 1920 in a message (e.g., CTX
message) granting a transmission opportunity to the user terminal
120. As shown in FIG. 19, the user terminal 120 may have planned
data for transmission 1906 that has a planned transmission duration
that falls short of the target transmission duration 1920. The user
terminal 120 may transmit a PPDU 1910 including base data (e.g.,
the data for transmission 1906) and may also transmit fill data
1908 according to a UL-MU-MIMO operating mode, during the
transmission opportunity, to fit the target transmission duration
1920. The AP 110 may determine and indicate the amount of fill data
for each user terminal 120 by transmitting trigger frames to the
user terminals 120. Alternatively, each user terminal 120 may
determine its own amount of fill data. In other embodiments, the
user terminal 120 may transmit the fill data 1908 prior to
transmitting the PPDU 1910. The fill data 1908 may include, for
example, end of file (EOF) padding delimiters, subframe pad octets,
or A-MPDU EOF subframes. The fill data 1908 may also be transmitted
before the PPDU 1910. In yet another embodiment, the fill data 1908
may be added to the beginning of an A-MPDU. A combined transmission
duration of the PPDU 1910, including the base data and the fill
data 1908, may fit the target transmission duration 1920.
FIG. 20 is a time sequence diagram 2000 that shows a user terminal
120 decreasing its transmission data rate, decreasing its level of
aggregation, and adding fill data 2008 to fit a target transmission
duration 2020 for a UL-MU-MIMO transmission during a transmission
opportunity. The dashed arrows in FIG. 20 indicate the change in
transmission duration resulting from the user terminal 120
increasing the level of aggregation and increasing the data rate
for the data for transmission 2006 to produce the PPDU 2010 as
transmitted by the user terminal 120. As described above, an AP 110
may indicate the target transmission duration 2020 in a message
(e.g., CTX message) granting a transmission opportunity to the user
terminal 120. As shown in FIG. 20, the user terminal 120 may have
planned data for transmission 2006 that has a planned transmission
duration that falls short of the target transmission duration 2020.
The user terminal 120 may decrease a level of data aggregation in
an A-MPDU or A-MSDU and may transmit the data 2006, with fill data
2008, at a lower data rate (e.g., by adjusting its MCS) to fit the
target transmission duration 2020. As discussed above, the AP 110
may determine and indicate the level of data aggregation and the
MCS for each user terminal 120 by transmitting trigger frames (not
shown for simplicity) to the user terminals 120. Alternatively,
each user terminal 120 may determine its own level of data
aggregation and MCS. A combined transmission duration of the PPDU
2010 and fill data 2008 may fit the target transmission duration
2020.
FIG. 21 is a time sequence diagram 2100 that shows a user terminal
120 increasing its transmission data rate, increasing its level of
aggregation, and adding fill data 2108 to fit a target transmission
duration 2120 for a UL-MU-MIMO transmission during a transmission
opportunity. The dashed arrows in FIG. 21 indicate the change in
transmission duration resulting from the user terminal 120
decreasing the level of aggregation and decreasing the data rate
for the data for transmission 2106 to produce the PPDU 2110 as
transmitted by the user terminal 120. As described above, an AP 110
may indicate the target transmission duration 2120 in a message
(e.g., CTX message) granting a transmission opportunity to the user
terminal 120. As shown in FIG. 21, the user terminal 120 may have
planned data for transmission 2106 that has a planned transmission
duration that exceeds the target transmission duration 2120. The
user terminal 120 may increase a level of data aggregation in an
A-MPDU or A-MSDU and may transmit the data 2006, with fill data
2008, at a higher data rate (e.g., by adjusting its MCS) to fit the
target transmission duration 2120. As discussed above, the AP 110
may determine and indicate the level of data aggregation and the
MCS for each user terminal 120 by transmitting trigger frames (not
shown for simplicity) to the user terminals 120. Alternatively,
each user terminal 120 may determine its own level of data
aggregation and MCS. A combined transmission duration of a PPDU
2110, including the data 2106, and the fill data 2008 may fit the
target transmission duration 2120.
FIG. 22 is a time sequence diagram 2200 that shows user terminals
120A-D concurrently transmitting data during a transmission
opportunity for a duration that fits a target transmission duration
2220. As described above, an AP 110 may indicate the target
transmission duration 2220 in a message (e.g., CTX message)
granting a transmission opportunity to the user terminals
120A-120D. As shown in FIG. 22, the user terminals 120A-120D may
transmit data (e.g., a PPDU or fill data) to fit the target
transmission duration 2220. The user terminal 120A may decrease a
level of data aggregation in an A-MPDU or A-MSDU (e.g., as
described above with respect to FIG. 17) and may transmit fill data
2208A and a PPDU 2210A to fit the target transmission duration
2220. The user terminal 120B may increase a level of data
aggregation in an A-MPDU or A-MSDU (e.g., as described above with
respect to FIG. 18) and may transmit fill data 2208B and a PPDU
2210B to fit the target transmission duration 2220. The user
terminal 120C may have data for transmission that fits the target
transmission duration 2220 without any modification or changes to a
corresponding PPDU 2210C. The user terminal 120D may transmit a
PPDU 2210D and fill data 2208D to fit the target transmission
duration 2220. In other embodiments, the user terminals 120 may use
any combination of the changes in data or operating and
transmission parameters shown in FIGS. 14-21 in order to fit the
target transmission duration. By maintaining each of the UL-MU-MIMO
transmissions (e.g., from user terminals 120A-120D) at the same
length, the power level of the transmissions may remain constant,
thereby reducing the negative effects of power fluctuations on the
receivers.
FIG. 23 is a flow chart depicting an operation for modifying data
and/or operating parameters such that a duration of an UL-MU-MIMO
transmission fits a target transmission duration. A user terminal
120 may send a request to transmit (e.g., an RTX) to an AP 110
(2301). The user terminal 120 may receive a wireless message (e.g.,
CTX) from the AP 110 indicating an uplink transmission opportunity
and a target transmission duration for each of a plurality of user
terminals 120 (2302).
The user terminal 120 may then fragment the data for transmission
(2303). In some aspects, the user terminal 120 may adjust its
transmission data rate to fit the target transmission duration
(2304). In other aspects, the user terminal 120 may adjust a level
of data aggregation to fit the target transmission duration (2305).
Still further, the user terminal 120 may add fill data to fit the
target transmission duration (2306). Each of the steps 2303, 2304,
2305, and 2306 may be optional. For some embodiments, the user
terminal 120 may perform any combination of these steps 2303-2306
to fit the target transmission duration (e.g., as described above
with respect to FIGS. 14-21). Finally, the user terminal 120 may
transmit a message over the target transmission duration
(2307).
In each of the above described embodiments, the user terminals 120
may perform uplink transmissions for the maximum duration indicated
by the AP 110. However, in accordance with other embodiments, one
or more of the user terminals 120 may transmit UL-MU PPDUs having a
duration shorter than the maximum duration indicated by the AP 110.
This may allow the user terminals 120 to conserve power and allow
other terminals more opportunities to transmit their uplink data
(e.g., as described above with respect to FIG. 19).
According to some example embodiments, the AP 110 may transmit a
CTX frame indicating at least: (i) which stations are clear to
transmit UL MU data, (ii) a starting time for the TXOP, and (iii)
an expected maximum duration for the transmission (e.g., in
accordance with CTX frames described above with respect to FIGS.
11-13). According to some embodiments, this CTX frame may be
preceded by RTS and ACK messages, as described above with respect
to FIG. 8. Similarly, with respect to FIG. 8, each of the user
terminals 120 targeted by the CTX frame may transmit data to the AP
110 starting at a time indicated by the CTX frame.
In accordance with some example embodiments, one or more of the
user terminals 120 may transmit data to the AP 110 for a duration
that is less than the requested maximum duration indicated in the
AP's CTX message. For some example embodiments (e.g., while
operating in accordance with MU-MIMO techniques), each user
terminal 120 may transmit data to the AP 110 for a duration that is
less than the requested maximum duration. However, in other example
embodiments (e.g., while operating in accordance with multi-user
OFDMA (MU-OFDMA)), user terminals 120 transmitting in the primary
channel may be required to maintain uplink data transmissions for
the requested maximum duration. For example, user terminals 120 may
transmit data to the AP 110 according to the example embodiments
described above with respect to FIGS. 14-22. Additionally, in some
embodiments, user terminals 120 requesting an immediate ACK or BA
may not end their transmissions before the requested maximum
duration has expired.
If a user terminal 120 completes its uplink transmission in less
than the requested maximum duration, the user terminal 120 may
inform the AP 110 of the expected duration of its transmission. The
AP 110 may conserve power and processing resources, for example, by
ceasing to decode information received from the user terminal 120.
However, if a user terminal 120 completes its uplink transmission
early, there is a risk that a legacy station may attempt to access
the channel after the uplink transmission has ended but before the
AP 110 has sent an ACK message. Accordingly, in some embodiments, a
user terminal 120 may include its uplink duration (e.g., the
maximum duration requested by the AP 110) in the legacy signal
(L-SIG) field of its uplink PPDU. Legacy devices receiving the PPDU
may then defer from channel access for the maximum duration
requested by the AP 110, even though the user terminal 120 may not
be transmitting for the entire duration.
The example embodiments recognize that, allowing responding user
terminals 120 to transmit data for a duration less than the maximum
duration indicated by the AP 110 may interfere with the timing of
ACK messages transmitted by the AP 110 to indicate uplink data was
correctly received. Therefore, in accordance with some embodiments,
each user terminal 120 may determine the expected duration of its
uplink data. This duration may be determined, for example, by
estimating the throughput and/or data rate of the communications
link between the user terminal 120 and the AP 110, and calculating
the time required to transmit the PPDU based on the estimated
throughput or data rate.
In accordance with some embodiments, user terminals 120 may
indicate the expected durations of their uplink data in uplink
PPDUs sent to the AP 110. In some example embodiments, the uplink
duration may be included within the legacy signal (L-SIG) field of
the PPDU. In other example embodiments, the uplink duration may be
included in the high efficiency signal (HE-SIG) A, B, or C fields.
In further example embodiments, the uplink duration may be included
in a MAC payload of the uplink PPDU, such as in a MAC header,
delimiter, or in a new frame. In other example embodiments, the
uplink duration may be included as a PHY delimiter added as a data
symbol after the end of the data payload of the user terminal data
to be transmitted.
In accordance with some other embodiments, the AP 110 may determine
the duration of an uplink PPDU from a user terminal 120 based on
information contained in the uplink PPDU. For example, the AP 110
may use the A-MPDU data length in the VHT-SIG-B field and the MCS
to determine the expected duration. In accordance with some other
embodiments, the AP 110 may use an indicated data length (e.g., an
A-MPDU data length) in combination with an estimated throughput of
the communications link between the user terminal 120 and the AP
110 to determine the expected uplink duration.
In accordance with further example embodiments, a user terminal 120
may include an end of frame (EOF) padding delimiter at the end of
an A-MPDU to indicate that the end of the uplink data has been
reached. An AP 110 may recognize the EOF padding delimiter, and
determine that the user terminal 120 has finished transmitting its
uplink data.
In accordance with some example embodiments, when a user terminal
120 is expected to complete its uplink transmission in a duration
less than the maximum duration requested by AP 110, the AP 110 may
use the expected time duration to adapt its decoding scheme in
order to avoid the case where multiple uplink data streams are
needed for decoding but one or more of the data streams terminates
in less than the requested maximum duration.
When one or more user terminals 120 completes its uplink
transmission in a duration less than the maximum duration requested
by the AP 110, the timing of the ACK messages transmitted by the AP
110 (e.g., to indicate uplink data was correctly received) may be
affected. For example, if all user terminals 120 complete their
uplink transmissions in less time than the maximum duration
requested by the AP 110, the AP 110 may send ACK messages earlier
than if the entire duration had been used. In accordance with some
embodiments, the AP 110 may send an ACK or BA (e.g., at least a
SIFS time) after the longest uplink transmission time among the
user terminals 120. In some examples, the AP 110 may determine the
longest transmission time among the user terminals 120 by receiving
an indication of the expected uplink duration from each of the user
terminals 120. In some other examples, the AP 110 may determine the
expected uplink durations of each of the user terminals 120 using
information provided in the uplink PPDUs. In further examples, the
AP 110 may determine the longest transmission time based on an EOF
padding delimiter received from each of the user terminals 120 when
the end of their uplink data is reached.
FIG. 24 depicts a time sequence diagram 2400 showing an example
frame exchange, according to some embodiments. AP 110 may send a
CTX message 2410 indicating that user terminals 120A, 120B, and
120C are each clear to initiate a respective uplink data
transmission having a maximum duration 2450. In response thereto,
user terminals 120A, 120B and 120C may transmit uplink data 2420A,
2420B, and 2420C, respectively. Each of the data transmissions
2420A, 2420B, and 2420C has a duration less than the requested
maximum duration 2450. Each data transmission may include
information indicating its expected duration, when the data
transmission is complete, and/or information from which the AP 110
may determine the expected duration (e.g., as described above for
some example embodiments). After all data transmissions are
complete, AP 110 may send ACK messages 2440A, 2440B, and 2440C to
user terminals 120A, 120B, and 120C, respectively. AP 110 may send
these ACK messages a SIFS time after the completion of the longest
data transmission (e.g., after data transmission 2420B, having a
duration 2425B).
In accordance with some other embodiments, the AP 110 may send a
termination message a SIFS time after the longest uplink
transmission time among the user terminals 120A-120C. The
termination message may indicate to the user terminals 120A-120C
that all user terminal data has been transmitted, and that the user
terminals should expect to receive an ACK or BA message from the AP
110. The AP 110 may then send the ACK or BA messages, either
immediately after sending the termination message or at a
predetermined time after sending the termination message.
FIG. 25 depicts a time sequence diagram 2500 showing another
example frame exchange, according to some embodiments. AP 110 may
send a CTX message 2510 indicating that user terminals 120A, 120B,
and 120C are each clear to initiate a data transmission having a
maximum duration 2550. In response thereto, UTs 120A, 120B, and
120C may transmit uplink data 2520A, 2520B, and 2520C,
respectively. Note that each of the data transmissions 2520A,
2520B, and 2520C has a duration less than the requested maximum
duration 2550. Each data transmission may include information
indicating its expected duration, when the data transmission is
complete, and/or information from which the AP 110 may determine
the expected duration (e.g., as described above for some example
embodiments). After all data transmissions are complete, AP 110 may
send termination messages 2530A, 2530B, and 2530C to user terminals
120A, 120B, and 120C, respectively, indicating that all data
transmissions have been completed, and indicating that the user
terminals 120A-120C should expect to receive an ACK or a BA message
from the AP 110. These termination messages may be sent a SIFS time
after the completion of the longest data transmission (e.g., after
data transmission 2520B, having a duration 2525B). Finally, at a
predetermined time after sending the termination messages, AP 110
sends ACK messages 2540A, 2540B, and 2540C to user terminals 120A,
120B, and 120C, respectively.
For some example embodiments (e.g., while operating in accordance
with MU-OFDMA techniques), the AP 110 may send an ACK message only
on the channel occupied by the longest user terminal transmission.
For some other example embodiments (e.g., while operating in
accordance with MU-OFDMA techniques), the AP 110 may send an ACK
message on each channel allocated for MU-OFDMA. In some aspects,
the AP 110 may verify that one or more channels are idle before
transmitting an ACK message on each channel allocated for MU-OFDMA.
For example, if a particular user terminal 120 completes its uplink
transmission before the longest user terminal transmission, the AP
110 may verify that the channel allocated to the particular user
terminal 120 is idle before sending an ACK message.
When a user terminal 120 completes its uplink transmission in less
than the maximum duration indicated by the AP 110, the user
terminal 120 may enter a sleep mode to conserve power. In
accordance with some example embodiments, a user terminal 120 which
completes its uplink transmission in less than the maximum duration
may send a CTS message to retain control of the channel until the
end of the requested duration (e.g., before entering a sleep mode
to conserve power). For example, if a user terminal 120 completes
its uplink transmissions at a time t.sub.u, and the requested
duration does not end until a later time t.sub.r, then, upon
completing its uplink transmissions, the user terminal 120 may send
a CTS message for the remaining duration (t.sub.r-t.sub.u), and
then enter the sleep mode.
Sleeping user terminals 120 may not receive ACK messages from the
AP 110. Thus, in example embodiments, user terminals 120 may wake
periodically or at predetermined time intervals to listen for an
ACK from the AP 110. In accordance with some example embodiments,
any user terminal 120 that ends its uplink transmissions in less
than the maximum duration may enter a sleep mode until the end of
the maximum duration, and then wake to listen for ACK messages from
the AP 110. An example of such an embodiment is depicted in FIG.
26, with respect to time sequence diagram 2600. In the example of
FIG. 26, UTs 120A-120C may complete their respective data uplink
transmissions 2620A-2620C in a duration less than a requested
maximum duration 2650. UT 120A completes its data transmission
first, and may send a CTS message 2625A to retain control of the
channel until the end of the requested maximum duration 2650. Then,
UT 120A may sleep for a duration 2630A, until the end of the
requested maximum duration 2650. Similarly, after UT 120B completes
data transmission 2620B, it may sleep for a duration 2630B, and
after UT 120C completes data transmission 2620C, it may sleep for a
duration 2630C, until the end of the requested maximum duration
2650. Once the maximum duration 2650 has elapsed, UTs 120A-120C may
wake and listen for the AP 110 to send ACK messages 2640A-2640C to
the UTs 120A-120C, respectively.
In some other example embodiments, the AP 110 and the user
terminals 120 may agree on a time interval, such that the AP 110
may only send an ACK message at multiples of the time interval.
User terminals 120 that complete their uplink transmissions early
may sleep and/or wake at multiples of this time interval to listen
for ACK messages from the AP 110. This time interval may be
specified, for example, in a CTX message 2610, or in beacon frames
transmitted by the AP 110. In some aspects, the time interval may
be global for all user terminals 120 associated with the AP 110, or
may be determined on an individual basis per user terminal 120. In
further embodiments, the AP 110 may specify in the CTX message 2610
one or more time durations where the AP 110 may potentially send an
ACK message if all user terminal transmissions have completed.
User terminals that complete their uplink transmissions early may
sleep and/or wake to listen for ACK messages at one or more of the
specified durations. An example of such an embodiment is depicted
in FIG. 27, with respect to time sequence diagram 2700. Note that
user terminals 120A-120C complete their respective data
transmissions 2720A-2720C in less than a maximum duration 2750.
User terminal 120A completes its data transmission first, and may
enter a sleep mode for a duration 2730A, and exit the sleep mode at
a first predetermined time interval 2731 to listen for an ACK
message from AP 110. If no ACK message is received (e.g., user
terminal 120B and user terminal 120C are still transmitting
respective data 2720B and 2720C during this time interval), user
terminal 120A may return to its sleep mode for a second
predetermined time interval 2732. When the second predetermined
time interval 2732 expires, user terminal 120B and user terminal
120C have completed respective data transmissions 2720B and 2720C
and entered a sleep mode for durations 2730B and 2730C,
respectively. After the predetermined time interval 2732, user
terminals 120A-120C wake and listen for AP 110 to send ACK messages
2740A-2740C.
According to some embodiments, the AP 110 may increase the chance
that a sleeping user terminal 120 is able to receive an ACK message
by transmitting the ACK message more than once. For example, the AP
110 may repeat a transmitted ACK message at least once, and a user
terminal 120 which was sleeping and failed to receive the ACK
message during the first transmission is more likely to be awake
during at least one of the subsequent transmissions.
According to some embodiments, an AP 110 may select one of the user
terminals 120 and require its uplink transmission to have the
maximum requested duration, while all other terminals 120 may be
allowed to end their uplink transmissions early and go to sleep.
Each of the user terminals 120 should be awake at the end of the
maximum time duration in order to receive an ACK message from the
AP 110.
FIG. 28 shows an illustrative flow chart depicting an example
operation 2800 for selective multi-user uplink (UL) communications.
Operation 2800 may be performed by a first wireless device, such as
any of UTs 120a-120i of FIG. 1, UT 120m or 120x of FIG. 2, a
wireless device 302 of FIG. 3, any of UTs 120A-120C of FIG. 8, or
24-27. The first wireless device may request permission to initiate
a UL transmission to a second wireless device (2801). In some
examples, the second wireless device may be an AP with which the
first wireless device is associated. For some embodiments,
requesting permission may include sending a request to transmit a
message to the second wireless device. The second wireless device
may, in some examples, acknowledge reception of the requested
permission.
The first wireless device may then receive, from the second
wireless device, permission to initiate the UL transmission
according to a MU UL protocol (2802). In some examples, the
permission to initiate the UL transmission may grant permission to
each of a plurality of wireless devices to initiate a respective UL
transmission.
The first wireless device may also determine a threshold duration
for the UL transmission (2803). The first wireless device may then
transmit UL data to the second wireless device in accordance with
the MU UL protocol and the threshold duration (2804). In some
examples, the threshold duration may equal a duration (or
substantially equal, such as a plus or minus tolerance) for
transmitting the UL data to the second wireless device. After
transmitting the UL data to the second device, the first wireless
device may, in some examples, enter a low-power state. For some
examples, the first wireless may exit the low-power state at a
predetermined time to receive an acknowledgment from the second
wireless device.
A person having ordinary skill in the art would understand that
information and signals can be represented using any of a variety
of different technologies and techniques. For example, data,
instructions, commands, information, signals, bits, symbols, and
chips that can be referenced throughout the above description can
be represented by voltages, currents, electromagnetic waves,
magnetic fields or particles, optical fields or particles, or any
combination thereof.
Various modifications to the implementations described in this
disclosure can be readily apparent to those skilled in the art, and
the generic principles defined herein can be applied to other
implementations without departing from the spirit or scope of this
disclosure. Thus, the disclosure is not intended to be limited to
the implementations shown herein, but is to be accorded the widest
scope consistent with the claims, the principles and the novel
features disclosed herein. The word "exemplary" is used exclusively
herein to mean "serving as an example, instance, or illustration."
Any implementation described herein as "exemplary" is not
necessarily to be construed as preferred or advantageous over other
implementations.
Certain features that are described in this specification in the
context of separate implementations also can be implemented in
combination in a single implementation. Conversely, various
features that are described in the context of a single
implementation also can be implemented in multiple implementations
separately or in any suitable sub-combination. Moreover, although
features can be described above as acting in certain combinations
and even initially claimed as such, one or more features from a
claimed combination can in some cases be excised from the
combination, and the claimed combination can be directed to a
sub-combination or variation of a sub-combination.
The various operations of methods described above may be performed
by any suitable means capable of performing the operations, such as
various hardware and/or software component(s), circuits, and/or
module(s). Generally, any operations illustrated in the Figures may
be performed by corresponding functional means capable of
performing the operations.
The various illustrative logical blocks, modules and circuits
described in connection with the present disclosure may be
implemented or performed with a general purpose processor, a
digital signal processor (DSP), an application specific integrated
circuit (ASIC), a field programmable gate array signal (FPGA) or
other programmable logic device (PLD), discrete gate or transistor
logic, discrete hardware components or any combination thereof
designed to perform the functions described herein. A general
purpose processor may be a microprocessor, but in the alternative,
the processor may be any commercially available processor,
controller, microcontroller or state machine. A processor may also
be implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
In one or more aspects, the functions described may be implemented
in hardware, software, firmware, or any combination thereof. If
implemented in software, the functions may be stored on or
transmitted over as one or more instructions or code on a
computer-readable medium. Computer-readable media includes both
computer storage media and communication media including any medium
that facilitates transfer of a computer program from one place to
another. A storage media may be any available media that can be
accessed by a computer. By way of example, and not limitation, such
computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or
other optical disk storage, magnetic disk storage or other magnetic
storage devices, or any other medium that can be used to carry or
store desired program code in the form of instructions or data
structures and that can be accessed by a computer. Also, any
connection is properly termed a computer-readable medium. For
example, if the software is transmitted from a website, server, or
other remote source using a coaxial cable, fiber optic cable,
twisted pair, digital subscriber line (DSL), or wireless
technologies such as infrared, radio, and microwave, then the
coaxial cable, fiber optic cable, twisted pair, DSL, or wireless
technologies such as infrared, radio, and microwave are included in
the definition of medium. Disk and disc, as used herein, includes
compact disc (CD), laser disc, optical disc, digital versatile disc
(DVD), floppy disk and Blu-ray disc where disks usually reproduce
data magnetically, while discs reproduce data optically with
lasers. Thus, in some aspects computer readable medium may comprise
non-transitory computer readable medium (e.g., tangible media). In
addition, in some aspects computer readable medium may comprise
transitory computer readable medium (e.g., a signal). Combinations
of the above should also be included within the scope of
computer-readable media.
The methods disclosed herein comprise one or more steps or actions
for achieving the described method. The method steps and/or actions
may be interchanged with one another without departing from the
scope of the claims. In other words, unless a specific order of
steps or actions is specified, the order and/or use of specific
steps and/or actions may be modified without departing from the
scope of the claims.
Further, it should be appreciated that modules and/or other
appropriate means for performing the methods and techniques
described herein can be downloaded and/or otherwise obtained by a
user terminal and/or base station as applicable. For example, such
a device can be coupled to a server to facilitate the transfer of
means for performing the methods described herein. Alternatively,
various methods described herein can be provided via storage means
(e.g., RAM, ROM, a physical storage medium such as a compact disc
(CD) or floppy disk, etc.), such that a user terminal and/or base
station can obtain the various methods upon coupling or providing
the storage means to the device. Moreover, any other suitable
technique for providing the methods and techniques described herein
to a device can be utilized.
While the foregoing is directed to aspects of the present
disclosure, other and further aspects of the disclosure may be
devised without departing from the basic scope thereof.
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